JP6897491B2 - Servo driver and state change detection method - Google Patents

Description

The present invention relates to a servo driver and a state change detection method.

A general servo driver that controls a servomotor is equipped with a notch filter in order to suppress mechanical resonance. The center frequency of this notch filter preferably coincides with the resonance frequency, but the resonance frequency changes with the aging of the machine. Therefore, the frequency response is calculated to detect the resonance frequency by controlling the servomotor based on the speed command obtained by adding the sinusoidal disturbance value to the original speed command, and the notch filter is adjusted based on the detected resonance frequency. When the detected resonance frequency is less than the reference resonance frequency, it has been proposed to notify the user of the necessity of inspecting the machine (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2016-34224

According to the above technique, it is possible to detect a secular change of a machine whose resonance frequency decreases. However, since the resonance frequency may increase due to aging, the above technique may not prevent the occurrence of mechanical resonance. Further, if a sinusoidal disturbance value is added to the speed command, the machine cannot be controlled as instructed by the host device.

Therefore, an object of the present invention is a technique capable of notifying the user that the state of the mechanical system has changed (aging deterioration) before mechanical resonance occurs regardless of the direction of change in the resonance frequency, and is a technique for being covered by a servomotor. The purpose is to provide a technology that does not adversely affect the behavior of the drive body.

In order to achieve the above object, the servo driver for controlling the servomotor of the present invention includes a servo control means for controlling the servomotor according to commands input in time series from an external device, and a servomotor drive itself. While the servo control means is performing the control according to the command in accordance with the command for the purpose of, the input data and the output data used for calculating the frequency response of the servo control means are collected in time series. , A calculation means for calculating the frequency response of the servo control means in the frequency range including the resonance peak based on the collected data, and a specific means for specifying the gain of the resonance peak from the frequency response calculated by the calculation means. And the gain specified by the specific means and a threshold value of less than 0 dB are compared, and when the gain is equal to or more than the threshold value, the servomotor and the driven body driven by the servomotor are included. It is provided with an information output means for outputting information for notifying the user that the state of the mechanical system has changed.

That is, the servo driver of the present invention identifies the gain of the resonance peak from the frequency response of the servo control means, and notifies the user that the state of the mechanical system has changed when the gain and the threshold value less than 0 dB are equal to or higher than the gain. It has a configuration to output information for the purpose of doing so. Mechanical resonance occurs after the resonance peak gain (hereinafter referred to as resonance peak gain) becomes 0 dB or more, and before the resonance peak gain becomes 0 dB or more, the resonance peak gain becomes a threshold value of less than 0 dB or more. Become. Therefore, according to the servo driver of the present invention, it is possible to notify the user that the state of the mechanical system has changed (aged deterioration) before the mechanical resonance occurs, regardless of the changing direction of the resonance frequency.

Further, the servo driver calculation means of the present invention follows a command intended to drive the servomotor itself, and while the servo control means is performing control according to the command, the frequency response of the servo control means. The input data and output data used for the calculation of are collected in chronological order. Here, "control according to the command according to the command for driving the servomotor itself" means control excluding the following control.
-Control according to the command input for the purpose of calculating the frequency response and automatically setting the control parameters-The input command is for the purpose of driving the servomotor itself, but the control is not as per the command. Control (control in which a sine wave disturbance value is added to the speed command, etc.)

Therefore, according to the servo driver of the present invention, the user is notified that the state of the mechanical system has changed (aged deterioration) before mechanical resonance occurs without adversely affecting the behavior of the driven body of the servomotor. Can be done.

For the servo driver of the present invention, various calculation means having different specific configurations (functions) can be adopted. For example, the calculation means "determines whether or not an amount of data for which the frequency response can be calculated has been collected based on the change pattern of the input data, and calculates the frequency response in the frequency range including the resonance peak. When it is determined that a possible amount of data has been collected, the data collection may be terminated and the frequency response of the servo control means may be calculated based on the collected data. ” Further, as a calculation means, the resonance peak performs a process of collecting data (input data and output data) for a predetermined time (or until a predetermined condition is satisfied) and then calculating a frequency response based on the collected data. A means of repeating until the frequency response of the included frequency range can be calculated may be adopted.

In order to prevent the gain of the non-resonant peak (the peak that is not the resonance peak) from being specified as the resonance peak gain, as a specific means, "the servo control means of the frequency response calculated by the calculation means". A means of "searching for the resonance peak and specifying the gain of the searched resonance peak from a frequency range having a frequency equal to or higher than the speed proportional gain, which is a control parameter, as the lower limit frequency" may be adopted. Further, when this specific means is adopted, the lower limit frequency may be set to a frequency equal to or higher than the threshold value in the closed loop transfer function of the speed feedback loop of the servo control means.

Further, in order to prevent the gain of the non-resonant peak from being specified as the resonance peak gain, the servo driver of the present invention states that "the servo control means includes a notch filter, and the specific means includes the calculation means. The resonance peak is searched for from the frequency range including the center frequency of the notch filter of the frequency response calculated by the above, and the gain of the searched resonance peak is specified. ” When this configuration is adopted in the servo driver of the present invention, the frequency range including the center frequency of the notch filter is set to be larger than the threshold value obtained from the center frequency, notch width and notch depth of the notch filter and the threshold value. It may be set as the frequency range of the notch filter in which the signal is greatly attenuated.

The input data and output data collected by the calculation means may be any data that can calculate the frequency response from them. The input data and the output data are data used for determining the input value and the output value of the gain (ratio of the input value and the output value), respectively. However, if the input data is "a current command that is a target value of the current value to be passed through the servo motor", when the input data uses data other than the current command (for example, a command input to the servo control means). Therefore, it is possible to obtain a frequency response in which the resonance peak gain can be satisfactorily specified. Therefore, the servo driver of the present invention states that "the servo control means controls the servomotor by generating a current command which is a target value of a current value to be passed through the servomotor based on the command, and the calculation means. Collects the current command generated by the servo control means as the input data. ”It is preferable to adopt the configuration. The output data is usually data indicating the position or speed of the servomotor, but the output data may be other data as long as the frequency response can be calculated by combining with the input data. good.

Further, the servo driver of the present invention is further provided with a threshold value calculation means for calculating the threshold value by adding a predetermined value to the gain specified for the first time by the specific means, and the information output means is described as described above. A configuration of "comparing each gain specified from the second time onward by the specific means with the threshold value calculated by the threshold value calculation means" may be adopted.

In the servo driver of the present invention, "the change rate of the gain specified this time by the specific means from the gain previously specified by the specific means was calculated, and the calculated change rate was equal to or higher than the change rate threshold value. In this case, it is also possible to add a "second information output means" that outputs information for notifying the user that the state of the mechanical system has changed. The rate of change calculated by the second information output means may be information in any unit.

In order to prevent erroneous determination of the state of the mechanical system (reduce the probability that the state of the mechanical system is erroneously determined), the servo driver of the present invention is provided with "according to the state of the driven body" as an information output means. A means of "switching the threshold value to be compared with the gain" or a means of "switching the threshold value to be compared with the gain according to one or more control parameters of the servo control means" may be adopted.

Further, in order to prevent erroneous determination of the state of the mechanical system due to noise, a means of "identifying the gain of the resonance peak from a plurality of frequency responses sequentially calculated by the calculation means" may be adopted as the specific means. good. It should be noted that the specific period of the gain by the specific means "specifying the gain of the resonance peak from the plurality of frequency responses calculated in time series by the calculation means" coincides with the calculation cycle of the frequency response by the calculation means. However, it may be longer than that. Further, the gain specification algorithm of the specific means "identifying the gain of the resonance peak from a plurality of frequency responses calculated in time series by the calculation means" is "calculating the moving average of the frequency response and from the calculation result. , Specify the gain of the resonance peak ", but remove the abnormal frequency response from the multiple frequency responses calculated in time series by the calculation means, and average the remaining frequency responses. Therefore, the gain of the resonance peak is specified. ”

Further, in the state change detection method of the present invention for detecting a state change of a mechanical system including a servomotor controlled by a servo driver and a driven body driven by the servomotor, a computer drives the servomotor. While the servo driver is performing control according to the command according to a command intended for itself, input data and output data used for calculating the frequency response of the servo driver are collected in chronological order. Based on the collected data, a calculation step of calculating the frequency response of the servo driver in the frequency range including the resonance peak, a specific step of specifying the gain of the resonance peak from the frequency response calculated by the calculation means, and the above-mentioned The gain specified by the specific means is compared with a threshold value of less than 0 dB, and when the gain is equal to or higher than the threshold value, information for notifying the user that the state of the mechanical system has changed is output. Perform the information output step and.

Therefore, according to the state change detection method of the present invention, the state of the mechanical system before mechanical resonance occurs without affecting the behavior of the driven body of the servomotor regardless of the change direction of the resonance frequency. Can be notified to the user that the frequency has changed (deteriorated over time). The "computer" in the state change detection method of the present invention may be a computer (control unit) inside the servo driver or a computer outside the servo driver.

According to the present invention, it is a technique that can notify the user that the state of the mechanical system has changed (aged deterioration) before mechanical resonance occurs regardless of the changing direction of the resonance frequency, and is a technique for notifying the user that the driven body of the servomotor It is possible to provide a technique that does not adversely affect the behavior of.

FIG. 1 is an explanatory diagram of a schematic configuration and a usage mode of the servo driver according to the first embodiment of the present invention. FIG. 2 is a flow chart of a first state determination process executed by an abnormality detection unit in the servo driver according to the first embodiment. FIG. 3 is a diagram for explaining the contents of the first state determination process. FIG. 4 is a flow chart of a second state determination process executed by the abnormality detection unit in the servo driver according to the second embodiment of the present invention. FIG. 5 is a diagram for explaining the contents of the second state determination process. FIG. 6 is a flow chart of a third state determination process executed by the abnormality detection unit in the servo driver according to the third embodiment of the present invention. FIG. 7 is a diagram for explaining the content of the third state determination process. FIG. 8 is an explanatory diagram of a method for limiting the resonance peak detection range. FIG. 9 is an explanatory diagram of a method for limiting the resonance peak detection range. FIG. 10 is an explanatory diagram of a servo system in which the resonance peak gain changes depending on the motor rotation direction.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<< First Embodiment >>
FIG. 1 shows a schematic configuration and a usage pattern of the servo driver 10 according to the first embodiment of the present invention.

The servo driver 10 according to the present embodiment is a device that controls a motor (three-phase motor) 30 for driving the driven body 35.

As shown in the figure, the servo driver 10 includes a control unit 11, an abnormality detection unit 12, and a power circuit 13 as main components. The power circuit 13 is a circuit that generates a three-phase alternating current supplied to the motor 30. The power circuit 13 includes, for example, a rectifier circuit for rectifying three-phase AC from a commercial power supply, a capacitor for smoothing the output voltage of the rectifier circuit, and a three-phase AC for the smoothed output voltage of the rectifier circuit. A circuit composed of an inverter circuit or the like for converting to voltage is used.

The control unit 11 is a power circuit so that the motor 30 operates according to a command (position command in this embodiment) input in time series from an external device (not shown) such as a PLC (Programmable logic controller). It is a unit that controls 13.

The control unit 11 is composed of a processor, a RAM, a flash ROM, a gate driver, and the like. Further, the flash ROM of the control unit 11 stores a program that the processor reads and executes on the RAM when the power of the servo driver 10 is turned on. Then, when the processor executes the program, the control unit 11 becomes a unit having various functional blocks such as a position control unit 21, a speed control unit 22, a notch filter 23, a current control unit 24, and a speed calculation unit 25. Function.

Each functional block included in the control unit 11 also has a control unit in the existing servo driver. Therefore, although detailed description of each functional block is omitted, the position control unit 21 is a position detected by a position detector (encoder) 31 attached to the motor 30 from a position command (hereinafter, referred to as a detection position). It is a unit (functional block) that calculates the speed command based on the position deviation obtained by subtracting. The position control unit 21 calculates a speed command using the set position proportional gain or the like.

The speed calculation unit 25 is a unit that calculates the speed of the motor 30 from the time change of the detection position. The speed control unit 22 generates a current command based on a speed deviation obtained by subtracting the speed calculated by the speed calculation unit 25 (hereinafter referred to as a detection speed) from the speed command calculated by the position control unit 21. Is. The position control unit 21 calculates the current command using the set control parameters such as the _{speed proportional gain k bp.}

The notch filter 23 is a digital filter for attenuating a signal having a frequency near the resonance frequency. A center frequency, a notch depth, and a notch width are set as control parameters in the notch filter 23. The current control unit 24 is a unit that feedback-controls the power circuit 13 so that the current according to the current command after passing through the notch filter 23 flows through the motor 30.

The abnormality detection unit 12 changes the mechanical system over time (aging deterioration) before the mechanical system (motor 30 and driven body 35) of the system composed of the servo driver 10, the motor 30, and the driven body 35 begins to vibrate. ) Is a unit for detecting. The abnormality detection unit 12 according to the present embodiment is implemented as a function of the control unit 11. However, the hardware (electronic circuit centered on the processor) that functions as the abnormality detection unit 12 may be provided in the servo driver 10 separately from the hardware for the control unit 11.

Hereinafter, the function of the abnormality detection unit 12 will be specifically described. In the following description, the portion including the control unit 11 and the power circuit 13 will be referred to as a servo control unit.

The abnormality detection unit 12 is a unit that repeatedly executes the first state determination process of the procedure shown in FIG. The abnormality detection unit 12 executes the first state determination process by controlling the power circuit 13 for the purpose of driving the motor 30 itself (according to a command for driving the motor 30 itself). This is a case where the control unit 11 performs control according to a command; hereinafter referred to as normal control). When the control unit 11 does not perform normal control (for example, when the control unit 11 controls the power circuit 13 to measure the frequency response of the servo control unit, or when control for automatically setting control parameters is performed. (When the control unit 11 is performing), the abnormality detection unit 12 waits for the normal control to be started by the control unit 11 without executing the first state determination process.

As shown in the figure, the abnormality detection unit 12 that has started the first state determination process first performs a data acquisition process (step S101).

In the data collection process, while monitoring the command current, the command current and the detection speed at each time are stored in the memory in the abnormality detection unit 12, and the desired amount of data can be collected from the command current monitoring result. This is the process of ending data collection when it is determined. Here, the desired amount of data is an amount of data that can calculate the frequency response in the frequency range including the resonance peak.

If the data collection process is a process that can collect the desired amount of data, even if it is a process of collecting data (command current and detection speed) in one continuous time zone, the data in a plurality of continuous time zones It may be a process of collecting data.

When the data collection process is completed, the abnormality detection unit 12 calculates the frequency response of the servo control unit from the collected data (step S102). Next, the abnormality detection unit 12 identifies the resonance peak gain from the calculated frequency response (step S103). That is, in step S103, the abnormality detection unit 12 searches for a resonance peak from the calculated frequency response, and performs a process of specifying the gain of the peak frequency of the searched resonance peak.

The abnormality detection unit 12 that has finished specifying the resonance peak gain _{determines whether or not the specified resonance peak gain is equal to} or greater than the threshold value gth (step S104). Here, the threshold value _gth is a value less than 0 dB (for example, −6 dB) preset in the abnormality detection unit 12.

Then, when the resonance peak gain is _{equal to or greater than the threshold value gth} (step S104; YES), the abnormality detection unit 12 performs the abnormality state processing (step S105). This abnormal state processing is a process that outputs information for notifying the user that the state of the mechanical system has changed (the resonance peak gain has become an abnormal value due to the change in the state of the mechanical system). good. Therefore, even if the processing for the abnormal state is a process of outputting a command for lighting / blinking the monochromatic LED provided in the housing of the servo driver 10, the color LED provided in the housing of the servo driver 10 is used. It may be a process of outputting a comment for lighting in a predetermined color. In addition, the abnormal state processing is a process for notifying the user that the state of the mechanical system has changed via an external device (that is, by transmitting predetermined information, the change in the state of the mechanical system is transmitted to the external device to the user. It may be a process of informing.

On the other hand, when the resonance peak gain is _{less than the threshold value gth} (step S104; NO), the abnormality detection unit 12 informs the user that the resonance peak gain has not become an abnormal value due to a change in the state of the mechanical system. Performs the normal state processing (step S106). This normal state processing only needs to be a processing that allows the user to know that no gain abnormality has occurred (the resonance peak gain has not become an abnormal value due to a change in the state of the mechanical system). Therefore, the normal state process is a process of outputting a command for turning off the monochromatic LED, but a process for outputting a command for turning on the color LED in a color different from the predetermined color. Is also good. Further, the normal state process may be a process of notifying the user that a gain abnormality has not occurred via an external device, or a process of not performing anything.

Then, the abnormality detection unit 12 that has completed the abnormal state processing or the normal state processing ends the current state determination processing and starts the next state determination processing.

As described above, the abnormality detection unit 12 operates. Therefore, the user of the servo driver 10, as shown in FIG. 3, when the resonance peak gain is increased to a value greater than the threshold value g _th due to aging of the mechanical system, resonance peak gain abnormality due to aging of the mechanical system It is possible to know that the value has reached a certain value (there is a possibility that vibration will occur in the mechanical system after a while). Then, if the user who knows that the mechanical system has changed over time (the resonance peak gain has become an abnormal value) performs maintenance of the mechanical system when the servo system is not in use, the state of the mechanical system will be changed over time. It can be returned (or brought closer to) the state before the change. Therefore, according to the servo driver 10 according to the present embodiment, it is possible to prevent vibration from being generated in the mechanical system during actual operation. Further, the abnormality detection unit 12 calculates the response frequency based on the current command and the detection speed while the control unit 11 is performing the normal control. Therefore, according to the servo driver 10, it is possible to notify the user that the state of the mechanical system has changed before the mechanical resonance occurs without adversely affecting the behavior of the driven body 35.

<< Second Embodiment >>
The servo driver according to the second embodiment of the present invention is a device having the same hardware configuration as the servo driver 10 according to the first embodiment. Therefore, in the following, the servo driver 10 according to the present embodiment will be described using the same reference numerals as those used in the description of the first embodiment. Further, in the following, for convenience of explanation, the servo driver 10 according to the nth (= 1 to 3) embodiment and the abnormality detection unit 12 in the servo driver 10 according to the nth embodiment will be referred to as the nth servo driver, respectively. It is also referred to as the 10th and nth abnormality detection unit 12.

The second servo driver 10 (servo driver 10 according to the second embodiment) repeatedly executes the second state determination process of the procedure shown in FIG. 4 in the first abnormality detection unit 12 of the first servo driver 10. This is a device replaced with the abnormality detection unit 12.

The processes of steps S201 and S202 of the second state determination process are the same as the processes of steps S101 and S102 of the state determination process (FIG. 2).

As described above, the first abnormality detection unit 12 executing the state determination process performs a process of specifying the resonance peak gain after the process of step S102. On the other hand, the second abnormality detection unit 12 executing the second state determination process determines whether or not N frequency responses have been calculated in the second state determination process this time after the process of step S202. Determine (step S203). Here, N is an integer of 2 or more preset in the second abnormality detection unit 12.

Then, when the calculation of N frequency responses is not completed (step S203; NO), the second abnormality detection unit 12 re-executes the processes of steps S201 and S202 to obtain the next frequency response. calculate.

When the calculation of N frequency responses is completed by repeating such processing (step S203; YES), the second abnormality detection unit 12 averages the N frequency responses to obtain an average frequency response. Is calculated (step S204). Note that averaging the N frequency responses means that the average value of the gains of the N frequency responses is obtained for each frequency.

Next, the second abnormality detection unit 12 identifies the resonance peak gain from the calculated average frequency response (step S205).

In short, in steps S201 to S205 of the second state determination process (FIG. 4), as schematically shown in FIG. 5, the average frequency is based on the calculation results of a plurality of (two in FIG. 5) frequency responses. The response is calculated, and the resonance peak gain is specified from the calculated average frequency response.

The processes of steps S206 to S208 of the second state determination process are the same as the processes of steps S104 to S106 of the state determination process (FIG. 2), respectively. That is, the second abnormality detection unit 12 _{determines whether or not the specified resonance peak gain is equal to} or greater than the threshold value gth (step S206). Then, the second abnormality detection unit 12 performs the abnormal state processing (step S207) or the normal state processing (step S208) based on the determination result.

As described above, the second abnormality detection unit 12 also has the same response frequency as the first abnormality detection unit 12 calculated based on the current command and the detection speed while the control unit 11 is performing normal control. The resonance peak gain is specified, and when the specified resonance peak gain is _{equal to or higher than the threshold value gth} , the user is notified that the mechanical system has changed over time. Therefore, the second abnormality detection unit 1
Like the servo driver 10 according to the first embodiment, the servo driver 10 according to the present embodiment provided with 2 may adversely affect the behavior of the driven body 35 regardless of the changing direction of the resonance frequency. Instead, it functions as a device that can notify the user that the state of the mechanical system has changed before mechanical resonance occurs.

Further, the second abnormality detection unit 12 calculates the average frequency response with a smaller amount of superimposed noise by averaging the N frequency responses, and specifies the resonance peak gain from the average frequency. Therefore, the servo driver 10 of the present embodiment has a mechanical state (resonance peak gain is an abnormal value) due to noise as compared with the servo driver 10 of the first embodiment in which the resonance peak gain is specified from one frequency response. It also functions as a device with a low probability that it will be erroneously determined.

<< Third Embodiment >>
The servo driver according to the third embodiment of the present invention is also a device having the same hardware configuration as the servo driver 10 according to the first embodiment. Therefore, in the following, the servo driver 10 according to the present embodiment will be described using the same reference numerals as those used in the description of the first embodiment.

The third servo driver 10 is a device in which the first abnormality detection unit 12 of the first servo driver 10 is replaced with a third abnormality detection unit 12 that repeatedly executes the third state determination process of the procedure shown in FIG.

The processes of steps S301 to S303 of the third state determination process are the same as the processes of steps S101 to S103 of the state determination process (FIG. 2).

As described above, the first abnormality detection unit 12 executing the state determination process determines whether or not _{the resonance peak gain is equal to or greater than the threshold value gth after the process of step S103.} On the other hand, in the third abnormality detection unit 12 executing the third state determination process, as shown in the figure, after the process of step S303, the resonance peak gain specified in the process is specified for the first time. It is determined whether or not it is a gain (hereinafter, referred to as the first specific gain) (step S304).

When the resonance peak gain specified this time is the first specified gain (step S304; YES), the third abnormality detection unit 12 is internally (on the memory in the third abnormality detection unit 12) with the resonance peak gain as a reference gain. ) (Step S305). Next, the third abnormality detection unit 12 internally stores the resonance peak gain and the current time identified this time as the pre-gain and the pre-evaluation time, respectively (step S310). Then, the third abnormality detection unit 12 ends the current state determination process and starts the next state determination process.

On the other hand, when the resonance peak gain specified this time is not the first specified gain (step S304; NO), the third abnormality detection unit 12 starts the processing after step S306. Then, the third abnormality detection unit 12 first calculates the amount of change of the resonance peak gain specified this time from the reference gain by subtracting the reference gain from the resonance peak gain specified this time in step S306. In step S306, the third abnormality detection unit 12 also calculates the rate of change of the resonance peak gain specified this time from the previously specified resonance peak gain. At this time, the unit of the calculated change rate is not particularly limited. For example, as shown in FIG. 6, the rate of change is "(resonance peak gain-pre-gain) / (current time-pre-evaluation time)", that is, the peak gain per real time (seconds, milliseconds, etc.). It may be the amount of change of. Further, the change rate may be a value obtained by dividing the amount of change in the peak gain by the amount of change from the previous evaluation time of the counter value (value counted up with the passage of time) of the energization time counter or the like.

After that, the third abnormality detection unit 12 satisfies at least one of the first condition that the calculated change amount is equal to or more than the change amount threshold value and the second condition that the calculated change rate is equal to or more than the change rate threshold value. It is determined whether or not it is satisfied (step S307). Here, the change speed threshold value is a value preset in the third abnormality detection unit 12 as a lower limit value of the change speed of the resonance peak gain for determining that the resonance peak gain has become an abnormal value. .. Further, the change amount threshold value is a value preset in the third abnormality detection unit 12 as a lower limit value of the change amount of the resonance peak gain from the reference gain for determining that the resonance peak gain has become an abnormal value. That is. The value of this change amount threshold value is determined so that the reference gain + change amount threshold value <0 dB is established unless the reference gain is an abnormal value.

When both or one of the first and second conditions is satisfied (step S307; YES), the third abnormality detection unit 12 performs the abnormality state processing of the above contents in step S308. Further, when the first and second conditions are not satisfied (step S307; NO), the third abnormality detection unit 12 performs the normal state processing of the above contents in step S309. The third abnormality detection unit 12 that has completed the abnormal state processing or the normal state processing internally stores the resonance peak gain and the current time identified this time as the pre-gain and the pre-evaluation time, respectively (step S310). Then, the third abnormality detection unit 12 starts the next third state determination process after completing the third state determination process this time.

As is clear from the above description, for the user of the third servo driver 10, when the resonance peak gain rises to "reference gain + change amount threshold"(<0 dB) due to aging of the mechanical system, the machine You will be notified that the system has changed over time. _{That is, as shown schematically in FIG. 7, the user is notified} of the mechanical system when the specified resonance peak gain is g c1 equal to or greater than the threshold value that matches the “reference gain + change amount threshold value”. You will be notified that aging has occurred.

By the way, there may be a problem in the mechanical system that the resonance peak gain changes suddenly in a short time, but if such a problem occurs in the mechanical system, the above notification function alone will cause the mechanical system. There is a risk that the mechanical system will begin to vibrate before the user is notified that aging has occurred. However, as described above, the third abnormality detection unit 12 of the third servo driver 10 indicates that the mechanical system has changed over time even when the change speed of the resonance peak gain is equal to or higher than the change speed threshold value. Notify to.

That is, for the user of the third servo driver 10, as is schematically shown in FIG. 7, even if the specified resonance peak gain g _c2 is less than the above threshold value, the previous resonance peak gain of _{g c2} the rate of change of the g _p is the case where the change rate threshold value or more is notified that the resonance peak gain due to aging of the mechanical system becomes an abnormal value. Therefore, according to the third servo driver 10, even if the above problem occurs in the mechanical system, the user is notified that there is a possibility that the mechanical system starts to vibrate before the mechanical system starts to vibrate. can do.

Hereinafter, some matters will be supplemented with respect to each of the above-described embodiments.

In the processes of steps S103, S204, and S303 of the first to third state determination processes (hereinafter referred to as gain specifying processes), the resonance peak is searched for from the entire frequency response (including the average frequency response) of the servo control unit. It may be a process of specifying the gain of the peak frequency of the searched resonance peak. However, in the gain identification process for searching the resonance peak from the entire calculated frequency response, the non-resonant peak (peak that is not the resonance peak) is searched for as the resonance peak, and the gain of the searched non-resonance peak is the resonance peak. It may be specified as a gain. In order to prevent such erroneous search (misidentification) from being performed, the gain identification process may be a process in which the detection range (search range) of the resonance peak is limited.

Various methods can be adopted as a method for limiting the detection range of the resonance peak. For example, the peak frequency of the resonance peak is higher than the _{velocity proportional gain k bp.} Therefore, the resonance peak may be searched from the frequency response on the frequency side higher than the velocity proportional gain k _bp.

Further, the frequency response of the servo control unit has a shape as shown in FIG. 3, that is, _{a frequency whose gain matches the threshold value gth} exists on the low frequency side, but the resonance frequency (resonance peak). The peak frequency of) is higher than _{the frequency f 0} on the low frequency side _{where the gain coincides with the threshold gth.} Then, the frequency f ₀ can be approximated by the following values from the closed loop transfer function of the speed feedback loop of the servo control unit.

Therefore, as shown in FIG. 8, the _{frequency in the frequency range from ak bp} to a frequency sufficiently higher than the resonance frequency, for example, the Nyquist frequency fn (1/2 of the reciprocal of the data acquisition cycle by the abnormality detection unit 12). The resonance peak may be searched for from the response.

Further, the center frequency of the notch filter 23 is usually adjusted to a value near the resonance frequency. Therefore, the detection range of the resonance peak may be set to a frequency range including the center frequency of the notch filter 23, for example, a frequency range included in the notch width.

Further, from the transfer function G (s) of the notch filter 23 described below, two frequencies whose attenuation rate coincides with the threshold value gth are obtained, and as shown in FIG. 9, the detection range of the resonance peak is between those frequencies. May be.

なお、この伝達関数Ｇ(ｓ)におけるＲ、ωａ、Ｑは、ノッチフィルタ２３の中心周波数ｆｃ［Ｈｚ］、ノッチ深さｄ［ｄＢ］、ノッチ幅ｗ［Ｈｚ］と、以下の関係を有する値である。

R, ωa, and Q in this transfer function G (s) have the following relationships with the center frequency fc [Hz], notch depth d [dB], and notch width w [Hz] of the notch filter 23. Is.

Further, in order to reduce the possibility that the state of the mechanical system is erroneously determined, the determination process of step S104 of the first state determination process and the determination process of step S206 of the second state determination process are performed at that time of the servo system. Depending on the situation, it may be a _{process of switching the threshold value gth} to be compared with the resonance peak gain (hereinafter, referred to as a threshold value switching determination process). The situation of the servo system at that time is the rotation direction of the motor 30, the control state of the control unit 11 specified by some control parameters, the inertia of the driven body 35, and the like.

Specifically, the driven body 35 driven by the motor 30 is not placed on the stage 36 on the outward route as shown in FIG. 10 (FIG. 10 (A)), and is an object on the stage 36 on the return route. Is placed (FIG. 10 (B)) in the case of a stage moving mechanism. In this case, the inertia of the driven body 35 changes depending on the rotation direction of the motor 30. That is, the resonance peak gain changes depending on the rotation direction of the motor 30.

Therefore, when the driven body 35 is a stage moving mechanism as shown in FIG. 6, if the threshold value _gth is fixed, the resonance peak gain is actually a normal (or abnormal) value. There is a possibility that an erroneous judgment will be made as an abnormal (or normal) value. Further, even if the control parameters of the control unit 11 (speed proportional gain k _bp, etc.) are changed or the inertia of the driven body 35 is changed, the resonance peak gain changes, so that the same erroneous determination is likely to occur. There is.

On the other hand, if the determination process of steps S104 and S106 is set as a threshold _{value switching determination process for switching the threshold value gth} to be compared with the resonance peak gain according to the situation at that time of the servo system, for example, the stage 36 moves in the first direction. When moving, the resonance peak gain is compared with the threshold value for moving in the first direction, and when the stage 36 is moving in the second direction opposite to the first direction, the resonance peak gain and the first It is possible to compare with the threshold value for two-way movement. Further, when the control unit 11 performs the first control in which the resonance peak gain is a relatively low value (when a control parameter group in which the resonance peak gain is a relatively low value is set in the control unit 11). For etc.), the first threshold value is used, and when the control unit 11 performs the second control in which the resonance peak gain becomes a higher value, a second threshold value higher than the first threshold value is used. When the control unit 11 performs the third control in which the resonance peak gain becomes a higher value, it is possible to use a third threshold value higher than the second threshold value.

Therefore, if the determination process in steps S104 and S106 is set as the threshold value switching determination process, it is possible to obtain the servo driver 10 with a lower probability that the state of the mechanical system will be erroneously determined.

The third abnormality detection unit 12 may be transformed into a unit that executes the third state determination process according to the status of the servo system. Specifically, for example, when the driven body 35 is a stage moving mechanism as shown in FIG. 6, the third abnormality detecting unit 12 is rotated when the motor 30 is rotating in the first direction. Is a unit that performs a third state determination process for the first direction, and performs a third state determination process for the second direction when the motor 30 is rotating in the second direction opposite to the first direction. It may be transformed into. Further, the control unit 11 has a first control in which the resonance peak gain is a relatively low value.
When performing the second control in which the resonance peak gain becomes a higher value and the third control in which the resonance peak gain becomes a higher value, the control unit 11 performs the first control on the third abnormality detection unit 12. When it is, the third state determination process for the first control is performed, and when the control unit 11 is performing the second control, the third state determination process for the second control is performed, and the control unit 11 performs the third control. When the above is performed, the third state determination process for the third control may be performed to transform the unit into a unit. If the third abnormality detection unit 12 is transformed into such a unit, a different reference gain will be used depending on the situation of the servo system, so that the probability that the state of the mechanical system will be erroneously determined can be reduced. Is possible.

Each of the above-mentioned abnormality detection units 12 is a unit that collects a current command and a detection speed (rotational speed of the motor 30) in order to calculate the frequency response. The output data may be any data whose frequency response can be calculated from them. However, as described above, if the input data is a current command, the resonance peak gain will be higher than when the input data uses data other than the current command (for example, the position command input to the servo driver 10). A well-identifiable frequency response can be obtained. Therefore, it is preferable that the input data is a current command. Further, the output data is usually data indicating the position or speed of the motor 30, but the output data may be other data as long as the frequency response can be calculated by combining with the input data. good. The input data and the output data are data used for determining the input value and the output value of the gain (ratio of the input value and the output value), respectively.

Further, instead of the processing of steps S101 and S102 of the first state determination processing, the processing of steps S201 and S202 of the second state determination processing, and the processing of steps S301 and S203 of the third state determination processing, "collect data. Therefore, the process of calculating the frequency response based on the collected data may be repeated until the frequency response in the frequency range including the resonance peak can be calculated.

The second state determination process (FIG. 4) is transformed from the N frequency responses into a process of identifying the resonance peak gain from the average of the remaining frequency responses by removing the abnormal frequency response by Thompson's rejection test method. You may. Further, the second state determination process may be transformed into a process of calculating the moving average of N frequency responses and specifying the resonance peak gain from the calculation result. Further, the third state determination process (FIG. 6) may be transformed into a process of specifying the resonance peak gain from the average of a plurality of frequency responses.

10 Servo driver 11 Control unit 12 Abnormality detection unit 13 Power circuit 21 Position control unit 22 Speed control unit 23 Notch filter 24 Current control unit 26 Speed calculation unit 30 Motor 31 Position detector 35 Driven body 36 Stage

Claims (13)

A servo driver that controls a servo motor
Servo control means that controls the servomotor according to commands input in chronological order from an external device, and
While the servo control means is performing control according to the command according to a command intended to drive the servomotor itself, input data and output data used for calculating the frequency response of the servo control means are input. A calculation means for calculating the frequency response of the servo control means in the frequency range including the resonance peak based on the collected data collected in time series.
A specific means for specifying the gain of the resonance peak from the frequency response calculated by the calculation means, and
A mechanical system including the servomotor and a driven body driven by the servomotor when the gain specified by the specific means is compared with a threshold value of less than 0 dB and the gain is equal to or higher than the threshold value. An information output means that outputs information for notifying the user that the state of the
A servo driver characterized by being equipped with. The specific means searches for and searches for the resonance peak from a frequency range in which a frequency equal to or higher than the speed proportional gain, which is a control parameter of the servo control means, of the frequency response calculated by the calculation means is set as the lower limit frequency. Identifying the gain of the resonant peak,
The servo driver according to claim 1. The lower limit frequency is a frequency equal to or higher than the threshold value in the closed loop transfer function of the speed feedback loop of the servo control means.
The servo driver according to claim 2. The servo control means includes a notch filter and includes a notch filter.
The specific means searches for the resonance peak from the frequency range including the center frequency of the notch filter of the frequency response calculated by the calculation means, and specifies the gain of the searched resonance peak.
The servo driver according to any one of claims 1 to 3, wherein the servo driver is characterized in that. The frequency range is the frequency range of the notch filter at which the signal is attenuated more than the threshold value, which is obtained from the center frequency, the notch width and the notch depth of the notch filter and the threshold value.
The servo driver according to claim 4. Based on the command, the servo control means generates a current command which is a target value of a current value to be passed through the servo motor to control the servo motor.
The calculation means collects the current command generated by the servo control means as the input data.
The servo driver according to any one of claims 1 to 5, wherein the servo driver is characterized in that. The calculation means determines whether or not an amount of data capable of calculating the frequency response has been collected based on the change pattern of the input data, and an amount capable of calculating the frequency response in the frequency range including the resonance peak. When it is determined that the data of the above has been collected, the data collection is terminated, and the frequency response of the servo control means is calculated based on the collected data.
The servo driver according to any one of claims 1 to 6, wherein the servo driver is characterized in that. A threshold value calculation means for calculating the threshold value by adding a predetermined value to the gain specified for the first time by the specific means is further provided.
The information output means compares each gain specified by the specific means after the second time with the threshold value calculated by the threshold value calculation means.
The servo driver according to any one of claims 1 to 7, wherein the servo driver is characterized in that. The rate of change of the gain identified this time by the specific means from the gain previously identified by the specific means is calculated, and when the calculated change rate is equal to or greater than the change rate threshold value, the state of the mechanical system. The servo driver according to any one of claims 1 to 8, further comprising a second information output means for outputting information for notifying the user that the speed has changed. The information output means switches the threshold value to be compared with the gain according to the state of the driven body.
The servo driver according to any one of claims 1 to 7, wherein the servo driver is characterized in that. The information output means switches the threshold value to be compared with the gain according to one or more control parameters of the servo control means.
The servo driver according to any one of claims 1 to 7, wherein the servo driver is characterized in that. The specific means identifies the gain of the resonance peak from a plurality of frequency responses calculated in time series by the calculation means.
The servo driver according to any one of claims 1 to 8, wherein the servo driver is characterized in that. A state change detection method for detecting a state change of a mechanical system including a servomotor controlled by a servo driver and a driven body driven by the servomotor.
The computer
While a command for driving the servo motor itself is being input to the servo driver, input data and output data used for calculating the frequency response of the servo driver are collected in time series, and the collected data. Based on the calculation step of calculating the frequency response of the servo driver in the frequency range including the resonance peak,
A specific step of specifying the gain of the resonance peak from the frequency response calculated by the calculation means, and
The gain specified by the specific means is compared with a threshold value of less than 0 dB, and when the gain is equal to or greater than the threshold value, information for notifying the user that the state of the mechanical system has changed is output. Information output steps to be performed and
A state change detection method characterized by executing.

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